It is written:
“So it was, when Moses had completed writing the words of this law in a book, when they were finished, 25 that Moses commanded the Levites, who bore the ark of the covenant of the LORD, saying: 26 “Take this Book of the Law, and put it beside the ark of the covenant of the LORD your God, that it may be there as a witness against you…” (Deuteronomy 31:24-26-24)
Was Moses the author of the Pentateuch (the first five Books of the Old Testament)? Scripture and secular history maintain this fact, even though many in our day and age deny it.
Consider the following evidence:
“There are several lines of evidence to indicate that Moses, the great lawgiver and deliverer of Israel who wrote the other four books of the Law, was the author of Genesis. (1) The earliest and continual tradition of the Jewish people, as recorded in the Talmud, attributes this book to Moses. (2) Moses is the only person we know of from this early time period who had the ability to write this book. The rest of the Israelites were a nation of uneducated slaves, whereas Moses was a highly educated son of the king (Acts 7:22). (3) Moses was the only one who had both the interest and information to write Genesis. Being Jewish Moses would have had access to the family records of his ancestors (cf. Gen. 5:1; 10:1; 25:19; etc.) which were no doubt brought down to Egypt by Jacob (Gen. 46). Since Moses was bent on delivering his people from Egypt, it is natural to assume that he was familiar with the promises of God passed down by his forefathers that God would indeed deliver them (cf. Gen. 46:3-4; Exod. 2:24). (4) Citations from Genesis show that the rest of the Old Testament regards it as part of the Law of Moses (Deut. 1:8; II Kings 13:23; I Chron. 1:1ff.). Since Moses was the author of the other “books of Moses,” as we will see later, it is reasonable to attribute the first book of Moses to him as well. (5) Jesus and the New Testament writers clearly regard Moses as the author of an essential part of Scripture (cf. Matt. 19:8; Luke 16:29; 24:27). We can conclude that Moses, using the family records which had been passed on to him, compiled the Book of Genesis.” (Norman Geisler, A Popular Survey Of The Old Testament, 610-623 (Kindle Edition); Grand Rapids, Michigan; Baker Books)
Regarding ancient Jewish testimony regarding this Mosaic authorship of the Pentateuch, consider the following:
“1B. R.H. Rfeiffer writes: ‘There is no reason to doubt that the Pentateuch was considered the divine revelation to Moses when it was canonized about 400 B.C.’ (Pfeiffer, JOT, 133) 1C. Ecclesiasticus, one of the books of the Apocrypha, written about 180 B.C., gives this witness: ‘All this is the covenant book of God Most High, the law which Moses enacted to be the heritage of the assemblies of Jacob’ (Ecclesiasticus 24:23 NEB). 2C. The Talmud (Baby Bathra, 146), a Jewish commentary on the Law (Torah) dating from 200 B.C., and the Mishnah (Pirqe Aboth, I, 1), a rabbinic interpretation and legislating dating from 100 B.C., both attribute the Torah to Moses. 3C. Likewise, Philo, the Jewish philosopher theologian born approximately A.D. 20, held Mosaic authorship: ‘But I will…tell the story of Moses as I have learned it, both from the sacred books, the wonderful monuments of his wisdom which he has left behind him and from some of the elders of the nation.’ (Philo, WP, 279) 4C. The first century A.D. Jewish historian Flavius Josephus writes in his Josephus Against Apion (11:18): ‘For we have not an innumerable multitude of books among us, disagreeing from and contradicting one another (as the Greeks have) but only 22 books (our present 39), which are justly believed to be divine; and of them, five belong to Moses, which contain his laws, and the traditions of the origin of mankind till his death.’ (Josephus, WFJ, 609)” (Josh McDowell, The New Evidence That Demands A Verdict, 458-459; Nashville, TN; Thomas Nelson Publishers).
While critics deny the Mosaic authorship of the Pentateuch, the testimony of Scripture and as supported by the evidence are clear.